Humans are adapted to view real objects in three dimensions (3-D). Electronically generated images, however, are generally only two dimensional (2-D). For example, the format of television and motion pictures presents images which appear only 2-D. The realism of these images would be greatly enhanced if the images could be presented so that they appear 3-D.
Many arrangements exist for presenting an image in three-dimensions. For example, a left-eye image and a right-eye image (for example, photographs of an object taken from two different perspectives) may be arranged in alternating vertical strips which are viewed through a stationary vertical parallax barrier. The parallax barrier permits the right eye of a viewer to view only the strips of the right-eye image and permits the left eye of a viewer to view only the strips of the left-eye image. Viewed separately, these left and right-eye images result in a single image which appears three-dimensional.
Alternatively, the strips of the left and right-eye images may be viewed through a stationary lenticular lens which focuses the strips of the left-eye image towards the left eye and the strips of the right-eye image towards the right eye. These arrangements are described and illustrated in U.S. Pat. No. 5,640,273.
There are several problems with the above-described parallax barrier arrangement. One problem is that a shift in the point of view of the viewer may deter viewing of the images. Another problem is that the narrowness of the slits in the parallax barrier reduces the amount of light reflected from the image strips which may pass to the viewer, reducing the brightness, and hence the visibility, of the image. The arrangement also only permits for viewing of a single static image.
Similar problems also exist when using a lenticular lens. For example, the field of viewing may be undesirably narrow and when arranged as described above, the image is static.
There have been numerous attempts at generating a series of images which appear three-dimensional. One method is to color encode images for separate presentation to the left and right eyes of a viewer. For example, color encoded left and right-eye motion picture images may be overlapped or interleaved and projected to a viewer. The viewer perceives the motion picture as 3-D when viewing the projected images through special glasses having two different colored lenses which "decode" the separate right and left-eye images.
This arrangement does not generate a true "autostereo" or automatic 3-D image in that, when viewed without the aid of the decoding glasses, the image does not appear three-dimensional. The arrangement requires all viewers to have special glasses or other equipment to perceive the image as three-dimensional. In addition, the quality of the image suffers because the true colors of the objects imaged are altered during the color encoding process and during viewing through the colorized lenses.
Other arrangements, such as that disclosed in U.S. Pat. No. 5,726,703, have similar drawbacks. In the arrangement disclosed in this patent, projected left and right-eye images are polarized at different angles. A viewer wears a pair of polarizing glasses to unite the left and right-eye images to generate a "3-D" image.
In general, these and other arrangements for generating perceived 3-D images all suffer from one or more drawbacks. Many of the arrangements are extremely complicated and/or expensive. Others do not lend themselves to viewing by more than one or a few viewers. Also, these arrangements interleave two spatially distinct images at a single point in time to generate each 3-D image, limiting the 3-D effect.
An improved method and apparatus for creating an autostereo image is desired.